I read alot everyday on investing but just wish i could remember a heck of alot more of what i read.
I have the same problem but a solution to it.
Read active:Summarize the chapters after you have read them. If you cant explain in your own words what you just read, you need to read it again or the time invested was useless. Take your time contemplating what you have read and how it connects to already known facts, maybe you even find that it conflicts with older knowledge. Take time to resolve those.
Take notes while reading:I nowadays always have a paper and a pencil that also serves as bookmark in the book im currently reading.
Taking notes includes to write down the chapters conclusion. It also anchores the new knowledge deeper in your brain.
I write my notes in a fashion like i would have nearly zero knowledge if i would read it in the future.
Be sure to note down the page of the book (and of course also the books title, author and ISBN for later reference).